Before moving into the work procedure of RCC slab casting, lets learn what are the equipment requirement and the scope of the work which are described below.
Materials and Machinery utilized:
- Transit Mixture
- Chute and CI Pipes
- Batching Point
Scope of the Work:
- Marking the slab
- Positioning the reinforcement
- Form work for the slab
- Positioning the concrete
The casting of RCC slab comprises of following three steps:
It has to be prepared according to the BBS arranged as per the approved drawing. The R/F shifting and binding has to be commenced right after shuttering is undertaken. R/F binding should persist as formwork.
a) Construction Joint
The construction joint might be pre chosen and settled before begining of the cementing/concreting. It is wanted to have two construction joints for principle building as chose. If there should be an occurrence of massive breakdown of the Batching plant, the extra Construction joint might be cleared out. The area of the construction joint should be at the 33% traverse. Construction joint should be straight and have profile of ‘L’shape so that progressive layer of the concrete might be impeccably reinforced with previous laid layer.
Arrangement of construction joint might incorporate roughening, expelling all laitance holding fast to the joint and utilization of thick slurry before begin of the new concrete.
b) Production and Placement of concrete
The stock of the materials has to be adequate to commence on the concrete. It has to be properly ensured by stores/purchase department that concreting is not halted on the account of necessary materials.
All plant, machineries and equipments are pre-checked and are put in working conditions.
Concrete of grade M-25 has to be created originating from out batching plant and straight pumped to the site of concrete positioning via the long pipeline. The pouring sequence should commence onwards from the grid A towards the direction of construction joint. Because the grade of concrete for column is M-40 and adjoining concrete is M-25, adequate offset adjacent to the column should be casted with M-40.The offset dimensions has to be given by PMC.
Proper walkways/platforms has to be created and organized so that the supports and upholding of the pipeline and manpower so not straightaway put pressure on and stand on the reinforcement.
Many carpenters as well as the supervisor has to thoroughly supervise and inspect the behavior and properties of the supports below the slab at the time of casting. Extra Props also have to be stacked down below the slab to give further supports in the cases of any failure or breakdown of supports.
The curing has to be commenced straight away after thumb set of the concrete laid down. Hessian clothe /Plastic has to be thoroughly covered over the set concrete to diminish the humidity and moisture evaporation from the concrete at the time of hardening and hence to reduce reduction of cracks. These cracks are the inheriting quality of the concrete which specifically shows through at the time of casting of the flat surfaces.